JP2006310429A - Thermal fuse-containing resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the evaporation of easily gasifiable components of a seal 4 to lessen or reduce the white smoke production to substantially null even under a high applied load of a fuse resistor for operating a thermal fuse 3 with heat generated from an abnormally energized resistor 2, wherein series connection body A of the resistor 2 with the thermal fuse 3 is housed in a heat-resistive case 1 having an opening, lead conductors 21, 31 of the body A are led out of slits 12, 13 of the case 1, and the seal 4 is filled in the case 1 with mainly an inorganic powder and a heat-resistive effect resin used as a binder. <P>SOLUTION: A heat transfer plate 5 contacts with the resistance element fuse 2 and extends over the thermal fuse 3 and is buried in the seal 4. This suppresses both the duration time of evaporation of water content of the seal and the evaporation quantity per unit time, thereby effectively preventing the white smoke from production. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resistor with a built-in thermal fuse.

The fuse resistor is used to prevent the occurrence of an accident such as a fire by interrupting energization when the resistance element is heated to a predetermined allowable temperature due to overcurrent. Thermal resistors with built-in thermal fuses as shown in (a) to (d) (for example, see Patent Document 1) are widely used.
FIG. 4 (a) is a longitudinal sectional view of a resistor with a built-in thermal fuse, FIG. 4 (b) is a cross sectional view of FIG. 4 (a), and FIG. (C) is a cross-sectional view of the ha-ha in FIG. 4 (a), and FIG. 4 (d) is a front view of the resistor with a built-in temperature fuse.

In FIG. 4, 1 ′ is a ceramic case having an opening. A ′ is a series connection body of the wire-wound resistance element 2 ′ and the cylindrical thermal fuse 3 ′, which is accommodated in the case 1 ′, and the lead conductor 21 ′ of the resistance element 2 ′ and the lead conductor 31 of the thermal fuse 3 ′. 'Is pulled out from the slits 12' and 13 'on the front side wall of the case.
4 ′ is a heat-resistant sealing material filled in the case 1 ′.

When an overcurrent flows through the temperature fuse built-in resistor, the resistor element generates heat, and the generated heat is released from the resistor element to the outside of the case, and the temperature is increased with a time constant determined by the thermal resistance and the heat capacity.
During this time, part of the heat generated by the resistance element is propagated to the thermal fuse via the connecting conductor between the resistance element and the thermal fuse and the sealing material portion between the resistance element and the thermal fuse, and the temperature fuse is also heated. To go.
When the temperature of the fuse element of the thermal fuse reaches the melting point, the melting of the thermal fuse is started, and when the melting is completed, the energization is cut off.
From the start of fusing to the completion of fusing, the resistance element continues to generate heat and the temperature continues to rise.However, when the fusing is completed, the resistance element stops generating heat and the amount of heat that has been charged according to the heat capacity is released. The whole is cooled to room temperature with a predetermined time constant.
The dotted line in FIG. 2 shows the temperature increase / decrease process.
The dotted line (A) in FIG. 2 shows the temperature rise / fall process of the resistance element, the dotted line (B) in FIG. 2 shows the temperature rise / fall process of the thermal fuse, and the time t ₀ is the start time of the temperature fuse operation, the temperature Ts is the operation start temperature of the thermal fuse, t ₁ is the time when the operation of the temperature fuse is completed, the temperature is increased with a predetermined time constant until the operation completion time t ₁ of the temperature fuse, and each time after the time t ₁ is predetermined The temperature falls with a time constant.
As shown in dotted line (c), sealing material heated even to time t _1, time t ₁ and later gradually lowering the temperature.
Temperature of heating-cooling of the sealing material is different depending on the location, because there is no heat propagation through the metal conductors from different resistive element and a temperature fuse, than the operating completion temperature T _R is the maximum temperature of the temperature fuse Can be kept at a low temperature.

  In the thermal fuse built-in type resistor, a cylindrical temperature fuse whose operating temperature (oil temperature when current is cut off in oil that rises by 1 ° C per minute at a current of 0.1 A or less) is approximately 135 ° C. The sealant is made of quartz powder as the main component and silicone resin as the binder, and the quartz powder is not carbonized and a heat-resistant material is selected for the binder. There is no problem of heat resistance on the carbonized surface.

However, since the sealing material is heated to 100 ° C. or higher when the operation of the thermal fuse is completed, easily vaporizable substances such as moisture in the sealing material are evaporated by this heating, and depending on the ambient temperature, the evaporation material The gas condenses and becomes mist, and there is a fear of being illusioned with the white smoke of a fire.
In particular, the silicone resin as the binder is produced by mixing and dispersing an uncrosslinked reactive silicone emulsion in an inorganic powder and dehydrating and condensing the silanol groups of the reactive silicone. The generation of the white smoke is remarkable.

  An object of the present invention is to accommodate a series connection body of a resistance element and a thermal fuse in a heat-resistant case having an opening, pull out a lead conductor of the series connection body from a slit of the case, and heat resistance is mainly composed of inorganic powder. In a fuse resistor that is filled with a sealing material with an effect resin as a binder and operates the thermal fuse with abnormal energization heat generation of the resistance element, even under high load application, from the sealing material It is intended to reduce or substantially reduce the generation of white smoke by suppressing evaporation of easily vaporized components.

  A resistor having a built-in temperature fuse according to claim 1 accommodates a series connection body of a resistance element and a temperature fuse in a heat-resistant case having an opening, and draws out a lead conductor of the series connection body from a slit of the case. In a fuse resistor in which a case is filled with a sealing material containing powder as a main component and a heat-resistant resin as a binder, and the temperature fuse is operated by the abnormal conduction heat of the resistance element, the temperature is in contact with the resistance element. A heat transfer plate extending on the fuse is embedded in the sealing material.

  The resistor with a built-in thermal fuse according to claim 2 is the resistor with a built-in thermal fuse according to claim 2, wherein the binder of the sealing material is a silicone resin.

  A resistor with a built-in thermal fuse according to a third aspect of the present invention is the resistor with a built-in thermal fuse according to the first or second aspect, wherein the heat transfer plate is a ceramic plate.

  A resistor with a built-in temperature fuse according to claim 4 is the resistor with a built-in temperature fuse according to any one of claims 1 to 3, wherein the temperature fuse is a cylindrical temperature fuse having an operating temperature of 110 ° C to 160 ° C. And

  A temperature fuse built-in resistor according to claim 5 is the temperature fuse built-in resistor according to any one of claims 1 to 4, wherein the case is made of ceramics having a bottom wall and a four-side wall, and the lead conductor of the temperature fuse It has a slit for drawing out and a lead conductor drawing-out slit of a resistance element on the front side wall.

  A resistor with a built-in thermal fuse according to claim 6 is characterized in that in the resistor with a built-in thermal fuse according to any one of claims 1 to 5, a shielding plate is embedded on the surface of the filling sealing material in the case opening. .

Even if a high load is applied to the fuse resistor and the encapsulant is heated, the encapsulant has heat resistance that is not carbonized by the heating, but there is no problem with heat resistance. When readily vaporizable components such as water are evaporated, depending on the ambient temperature, water vapor may condense and atomize, resulting in the illusion of white smoke from fire.
However, due to the heat transfer plate, the heat generated by the resistance element is quickly transmitted to the thermal fuse, so that the thermal fuse is blown quickly, and the heating time of the sealing material is shortened and the thermal fuse is transmitted to the thermal fuse to increase the temperature. The amount of heat transmitted to the sealing material side is reduced by the amount of heat released to the outside through the lead conductor of the fuse, so that the temperature rise of the sealing material can be kept low. As a result, both the heating time and the heating temperature of the sealing material are reduced.
Therefore, both the evaporation duration time of moisture from the sealing material and the evaporation amount per unit time can be suppressed, and the generation of white smoke can be effectively prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A is a longitudinal cross-sectional view of an embodiment of a resistor with a built-in thermal fuse according to the present invention, FIG. 1B is a cross-sectional view of FIG. 1A, and FIG. ) Is a cross-sectional view of FIG. 1 (a), and FIG. 1 (d) is a front view of the same embodiment.
In FIG. 1, reference numeral 1 denotes an upper open case made of heat-resistant material such as ceramics, which has a low wall and four side walls, and lead conductor insertion slits 12 and 13 are provided on the front side wall.
Reference numeral 2 denotes a resistance element. Cap electrodes with lead conductors are attached to both ends of a heat-resistant core such as ceramics, resistance wires are wound on the core, and both ends thereof are connected to each cap electrode by welding or the like.
Reference numeral 3 denotes a thermal fuse, for example, a cylindrical thermal fuse, in which a lead conductor is welded to both ends of a fuse element made of a fusible alloy piece, a flux is applied to the fuse element, and a heat-resistant cylinder, for example, ceramics is applied on the flux-applied fuse element. The tube is inserted, and the space between both ends and each lead conductor is sealed with a heat-resistant sealing material, for example, an epoxy resin containing an inorganic filler.
As this cylindrical thermal fuse, one having an operating temperature (oil temperature when energization is interrupted in oil that rises 1 ° C. per minute at a current of 0.1 A or less) 110 ° C. to 160 ° C. is used.
The resistance element 2 and the thermal fuse 3 are connected in series at the other lead conductors 211 and 311 so that the distance between the one lead conductors 21 and 31 is a predetermined distance. This connection can be made by welding, and in order to prevent thermal damage to the fuse element of the thermal fuse, the other lead conductor 311 of the thermal fuse 3 is made sufficiently long and short-time welding, for example, spot welding. Resistance welding, laser welding, etc. are used. A caulking connection or a torsional connection can also be used.
The resistance element / thermal fuse connection body A is accommodated in the case 1, and the lead conductor 21 of the resistance element 2 and the lead conductor 31 of the thermal fuse 3 are drawn out from the slits 12 and 13.
Reference numeral 4 denotes a sealing material filled in the case 1, in which a curable resin binder is blended with the inorganic powder. As the inorganic powder, powdered quartz, alumina, mica, zirconia, titanium dioxide or the like can be used, and a silicone resin can be used as the binder. The amount of inorganic powder is 80% by weight or more, and the amount of silicone resin is 1 to 4% by weight.
In order to fill the case 1 with the sealing material 4, an inorganic powder, a silicone emulsion and a catalyst (salts such as tin, zinc, iron, lead and organic amine acid) are mixed and injected into the case. The silicone emulsion is cured at room temperature or under heating. This curing is based on cross-linking by dehydration condensation reaction of silanol groups, and water is generated.
In FIG. 1, reference numeral 5 denotes a heat transfer plate embedded in the filling sealing material 4, which is in contact with the resistance element 2 and extends onto the thermal fuse 3, and the outer shell is equal to the inner shell of the case. There are small dimensions. It is preferable to bring the heat transfer plate 5 into contact with the thermal fuse 3 as well.
As the material of the heat transfer plate 5, a material having higher thermal conductivity than the sealing material 4 is used. For example, a ceramic plate, an aluminum plate, or a copper plate can be used.

  In order to fabricate this temperature fuse built-in type resistor, the resistor 1 and the temperature fuse serially connected body A are accommodated in the case 1, and the lead conductors 21 and 31 are applied to the bottoms of the slits 12 and 13 on the front side wall of the case. The position of the element 2 and the thermal fuse 3 is determined, the sealing material 4 is injected up to the top level of the resistance element 2, and then the heat transfer plate 5 is fitted into the case 1, and further the sealing material 4 is injected, After all the encapsulant is cured, the production is finished.

When a high load is applied to the resistor with a built-in thermal fuse, the resistive element generates heat, and the resistive element, the thermal fuse and the sealing material are heated up. When the thermal fuse reaches the operation start temperature Ts, the fuse element The alloy is melted, and the molten alloy is divided into spheroids after time Δt due to wetting and spreading to the end portion of the lead conductor due to surface tension, and the operation for shutting off the thermal fuse is completed. In addition, both the sealing material and the temperature change are changed.
In FIG. 2, the dotted line (A) indicates the temperature rising / falling state of the resistance element of the conventional temperature fuse built-in resistor, that is, the resistor with a built-in temperature fuse not embedded in the heat transfer plate, and the dotted line (B) indicates the same temperature fuse. The temperature rise / fall state of the built-in resistor thermal fuse, the dotted line (C) shows the temperature rise / fall state of the encapsulant of the temperature fuse built-in resistor, and the time t ₀ starts the operation of the temperature fuse The time Ts is the operation start temperature of the temperature fuse, and t ₁ is the operation completion time of the temperature fuse after Δt with respect to the time t ₀ .
In FIG. 2, the solid line (A ′) indicates the temperature rise / decrease state of the resistance element of the temperature fuse built-in resistor according to the present invention, that is, the temperature fuse built-in resistor embedded in the heat transfer plate, and the solid line (B ′) indicates the temperature rise / fall state. also the Atsushi Nobori, cooling conditions of a temperature fuse temperature fuse embedded resistor, a solid line (c ') is also shown a heating-cooling state of the sealing material temperature fuse embedded resistor, respectively, the time t _0' is The time when the operation of the thermal fuse is started, t ₁ ′ is the time when the operation of the thermal fuse is completed.

In the temperature fuse built-in resistor according to the present invention, since the heat transfer plate from the resistance element to the temperature fuse is embedded in the sealing material, heat propagation from the resistance element to the temperature fuse is efficiently performed, Since the temperature fuse is heated more quickly than the conventional resistor with a built-in temperature fuse, the time when the temperature fuse reaches the operation start temperature Ts as shown by the time t ₀ ′ of the solid line (b ′) in FIG. faster than the time t ₀ of the conventional thermal fuse embedded resistor, and following this, as shown by the solid line in FIG. 2 (b ') t _1' and when the temperature fuse reaches the operation completing temperature There faster than the time t ₁ of the conventional thermal fuse embedded resistor, therefore, the operation of the thermal fuse is completed as apparent from the comparison of the solid line in FIG. 2 (b ') and a dotted line (b) Until the heating time of the sealing material It is shorter than time fuse embedded resistor.
In the temperature fuse built-in resistor according to the present invention, the amount of heat propagated from the resistance element to the temperature fuse among the heat generated by the resistance element increases due to the heat transfer plate, and the lead conductor of the temperature fuse is transferred from the temperature fuse. Since the amount of heat released to the outside increases (+ ΔQ), the amount of heat transmitted from the resistance element to the sealing material is reduced by that amount (+ ΔQ), and the dotted line (c) and solid line (c ′) in FIG. 2 are compared. As is clear from the above, the heating temperature of the sealing material is lowered accordingly.
Therefore, since the time for heating the sealing material and the heating temperature are both reduced by the heat generation of the resistance element, the evaporation of moisture can be well prevented and the generation of white smoke can be sufficiently reduced.

3A is a longitudinal sectional view of another embodiment of the resistor with a built-in thermal fuse according to the present invention, FIG. 3B is a cross sectional view of FIG. (C) in FIG. 3 is a cross-sectional view taken along the line ha, FIG. 3 (d) is a front view of the same embodiment, and in the embodiment shown in FIG. An airtight shielding plate 6 for blocking evaporation of water vapor or the like is embedded on the surface of the material.
If the material of the hermetic shielding plate 6 is made to have better thermal conductivity than the sealing material 4, it is possible to suppress the temperature rise of the sealing material due to its good heat dissipation and to more effectively prevent evaporation of water and the like. For the hermetic shielding plate, for example, a ceramic plate, an aluminum plate, or a copper plate is preferably used.
In FIG. 3, the same reference numerals as those in FIG. 1 denote the same components.

The open case is made of ceramic with a length of 25 mm, width of 14 mm, and height of 9.0 mm, the resistance element is a 10 Ω winding type resistor with an outer diameter of 4.6 mmφ, the thermal fuse has an operating temperature of 135 ° C., and the outer diameter is 2 A cylindrical thermal fuse of 0.5 mmφ was used. The lead conductor diameter of the thermal fuse was 0.6 mmφ, the lead conductor diameter of the resistance element was 0.8 mmφ, and the distance between the lead conductors was 5.5 mm.
96% alumina ceramic plate with a length of 18.5mm, a width of 10.2mm, and a thickness of 0.8mm is used for the heat transfer plate. It was used.
This thermal fuse built-in resistor has a rating of 1.6 W.
When a load of 250 W was applied at room temperature of 25 ° C. (number of samples: 20), generation of smoke weaker than the rising smoke of incense was only observed for 6.0 to 7.0 seconds.
On the other hand, in the case of omitting the shielding plate, generation of smoke more than cigarette smoke continued for 13.9 seconds to 14.6 seconds, and there was a high probability that it would be an illusion of fire.

1 is a view showing an embodiment of a temperature fuse built-in resistor according to the present invention. 6 is a diagram showing temperature changes of a resistance element, a thermal fuse, and a sealing material when an overload is applied between the resistor with a built-in temperature fuse according to the present invention and a conventional resistor with a built-in temperature fuse. It is drawing which shows another Example of the resistor with a built-in temperature fuse which concerns on this invention. 1 is a diagram illustrating a conventional resistor with a built-in thermal fuse.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 12 Slit 13 Slit 2 Resistive element 21 Resistive element lead conductor 3 Thermal fuse 31 Thermal fuse lead conductor 4 Sealing material 5 Heat transfer plate 6 Shielding plate

Claims (6)

A series connection body of a resistance element and a thermal fuse is accommodated in a heat-resistant case having an opening, a lead conductor of the series connection body is drawn out from a slit of the case, and inorganic powder is a main component and a heat-resistant resin is used as a binder. In a fuse resistor in which a sealing material is filled in a case and a thermal fuse is operated by abnormally energizing heat generation of the resistive element, a heat transfer plate that contacts the resistive element and extends on the thermal fuse is sealed Thermal fuse built-in resistor characterized by being embedded inside. 2. The thermal fuse built-in resistor according to claim 1, wherein the binder of the sealing material is a silicone resin. 3. The temperature fuse built-in resistor according to claim 1, wherein the heat transfer plate is a ceramic plate. The temperature fuse built-in resistor according to any one of claims 1 to 3, wherein the temperature fuse is a cylindrical temperature fuse having an operating temperature of 110 ° C to 160 ° C. 5. The case according to claim 1, wherein the case is made of ceramics having a bottom wall and a four-side wall, and has a lead conductor lead slit for the thermal fuse and a lead conductor lead slit for the resistance element on the front side wall. Temperature fuse built-in resistor. 6. The thermal fuse built-in resistor according to claim 1, wherein a shielding plate is embedded on the surface of the filling sealing material in the case opening.

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